OTUD3-mediated deubiquitination licenses TEX264 to orchestrate ER-phagy for KDM5B degradation in teniposide lung cancer therapy.

High expression of Lysine-Specific Demethylase 5B (KDM5B) in lung cancer drives tumorigenesis and immunosuppression. KDM5B is negatively correlated with endoplasmic reticulum (ER)-phagy receptors such as TEX264, indicating that selective induction of ER-phagy may degrade KDM5B. Our work revealed that chemotherapeutic drug Teniposide (Ten) was a potent anti-lung cancer agent, which could increase the stability of TEX264. The present study aims to elucidate the critical target and mechanism by which Ten inhibits KDM5B through TEX264-associated ER-phagy against lung cancer. Ten exhibited potent lung cancer suppression ability, as evidenced by the weakened proliferation of organoids and tumor grafts in mice along with activation of the immune microenvironment. Highly-expressed KDM5B demonstrated down-regulation upon Ten treatment, which may be attributed to its degradation via ER-phagy. Blockage of ER-phagy weakened Ten-mediated KDM5B degradation. Insightful investigations discovered that Ten activated OTUD3, a deubiquitylase, which stabilized TEX264, a crucial receptor for ER-phagy. Notably, genetic knockdown of TOP2A impacted little on the Ten-mediated ER-phagy. OTUD3 silencing dampened Ten-driven ER-phagy and KDM5B inhibition. To summarize, these findings demonstrate that Ten effectively inhibits lung cancer and activates immunocytes by KDM5B inhibition, which is regulated by TEX264-associated ER-phagy. Most importantly, OTUD3 serves as an essential target for enhancement of TEX264 stabilization.